Aircraft tracking and indicating system



Oct. 6, 1964 M. RODGERS AIRCRAFT TRACKING AND INDICATING SYSTEM 5 Sheets-Sheet 1 Filed Jan. 27, 1961 INVENTOR. LIONEL MONTGOMERY RODGERS ATTORNEY OCL 6, 1964 1 M. RODGERS 3,152,315

AIRCRAFT TRACKING AND INDICTING SYSTEM Filed Jan. 27, 1961 5 Sheets-Sheet 2 1.12 1.11 1.22 1.21 1.32 1.31 L42 1.41 S S 6 S C '1 1' 1 1 rx 1: 1 in 1w xs F I G 4 G ".1 1.,/ n'.- ..vl x,..- -..Y/ .J 1.13 1: 1.23 C: L33() 1.43 'C5 F16 4b 1 C 1 FIG. 4c 1 [a 1.21 1.41

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1.1011151. MONTGOMERY RoDGERs ATTORNEY ct 5, 1964 L. M. RODGERS 3,152,315

AIRCRAFT TRACKING AND INDICATING SYSTEM Filed Jan. 27, 1961 5 Sheets-Sheet 3 UL fao INVENTOR. LIONEL MONTGOMERY RODGERSv BY FIG. 5 fam M2M ATTORNEY Oct. 6, 1964 1 M. Ronal-:RS 3,152,315

AIRCRAFT TRACKING AND INDICATING SYSTEM Filed Jan. 27, 1961 5 Sheets-Sheet 4 RAI RAZ RAS RA4 l RA5 fsao' FIG@ . FNVENTOR. LIONEL MONTGOMERY RODGERS /Zumc ATTORNEY Oct- 6, 1964 L. M. RODGERS 3,152,315

AIRCRAFT TRACKING AND INDICATING SYSTEM Filed Jan. 27, 1961 5 Sheets-Sheet 5 RDbO-Q RD-Q RDfjo-Q I DDI DD2 DB3 :m D05 i 1 @I I 1 I To RELAY AssEMm 0 1 702 0 1 I o1 F01 coNrRoLLED HOLDING lRc n' fsw Y INVENTOR. LLM` LIGQEL MONTGOMERY RODGERS FIG. 8 um 1&1,

ATTORNEY United States Patent Office 3 l 52 ,3 l5 Patented Oct. 6, 1964 3,152,315 AIRCRAFT TRACKING AND INDCATING SYSTElvl Lionel Montgomery Rodgers, Norwalk, Conn., assigner to Laboratory for Electronics, Inc., Boston, Mass., a corporation of Delaware Filed Jan. 27, 1961, Ser. No. 85,413 12 Claims. (Cl. 340-23) The present invention relates to a trafc indicating system or traic surveillance system, particularly adapted for use in connection with trac at or on an airport or other restricted facility, and particularly for providing a system which will detect presence of a vehicle, such as a surface vehicle or an airborne vehicle, when entering upon or into a controlled area such as an ascent or descent air corridor adjacent to a runway, or a runway or taxi strip and upon continuation of such vehicle along the corridor or runway to determine and provide an indication of the direction of travel of such vehicle in or along such corridor or runway and to track such detected vehicle through actuation of the vehicle itself, such indication made remotely as on a display panel or on a miniature layout of such air corridor and runway and to terminate through an actuation of the vehicle itself at a point of departure from the air corridor, runway, or taxi strip. The size of vsome present day air terminals or airports precludes visual observation of the entire operations on the airport even during daylight hours and particularly when weather conditions reduce visibility. During the hours of darkness visual observation of operations at such facilities is substantially reduced while inclement weather, which may of itself not necessitate reduction of operations at such facility, may further reduce visual information about operations during such hours of darkness.

Flight and navigational aids, within aircraft themselves and other aids located at or near an airport, permit ight operations from airports during weather conditions which normally inhibit visual access to the entire operations on an airport. The size, and in particular the length, of present day runways sometimes places the point of takeolf of aircraft at substantial distances from the control tower. Thus the distance at which aircraft operations are taking place from the tower, aggravated by inclement weather conditions and further aggravated by limited night vision, at times precludes actual visual observation of operations.

Under such conditions, other means of determining the position of vehicles using the airport must be relied upon, as for example, radio communication between the aircraft and the control tower, or observation of operations by radar or other complex means, generally located on or near the airport. Radio communication between aircraft and the tower is limited since, practically, communication can be between only two principals at one time. Where two or more aircraft are on the ground or in the vicinity of an airport and each is trying to contact the tower of the airport to report its position, for example, one aircraft must wait for the other aircraft to finish its report to the tower before entering into its own conversation with the tower to report its own position.

Heavy aircraft traiiic requires extensive communication between aircraft and the control tower even on days when weather conditions permit visual observation of the entire operations on and above the airport. On days when weather conditions reduce visibility and at night when vision is limited by darkness, radio communications between aircraft and the control tower is greatly increased so that often the capacity of the airport is limited by the capacity of the radio communications channel or channels.

Several types of surface surveillance systems have been proposed, including the use of radar to sweep the entire airport and to indicate traffic thereon. Generally, such systems indicate pictorially the operations on an airport on an instantaneous basis which necessitates substantially constant observation of the pictorial receiver. The image provided by such radar system must be interpreted by visual observation since such surface surveillance system itself does not direct attention to particular conditions, operations and events occuring, nor in particular, direct attention to potentially dangerous conditions which may occur on and above the airport.

The present invention may, very well, be employed as supplementary equipment on an airport where such surface surveillance system may be in use. The combination of such surface surveillance system and the present invention at an airport would provide very little overlap of information since one system would complement the other rather than provide duplicated information.

Where a radar surface surveillance system may show pictorially the operations on the surface of the airport the present improved traffic indicating system will provide indications of such operations which may be presented on a miniature layout on the airport itself so as to indicate approximate positions of aircraft operating on and above the airport and will provide alarms directing the attention of the traffic director to potentially dangerous occurrences on the airport itself.

When used as the sole indicating system of airport traflic, the present invention provides a greatly improved traffic indicating system for use at an airport or air terminal which indicating system operates through actuation of the traic itself, which may be on the surface of the airport, airborne in the ascent or descent corridors leaving or approaching a runway, or somewhat above the runway, for example. Continued indication of the indicating system is dependent upon actuation, by the initiating vehicle, of spaced detection stations between initiation and ultimate termination, and termination of indication of the indicating system is made through actuation of one of the termination sections by the same vehicle.

The present invention provides a detection system, including a series of detection stations which in effect sectionalize a predetermined pathway which may be all or part of an ascent or descent corridor from and to a runway, the runway itself, and/ or the normal taxi strips, or taxi ways 0f an airport. Each detection station may iriclude one or more detection devices, a relay assembly, detection 'and direction indicators and certain alarms with the indicators and alarms associated with a display panel which may be a miniature layout of the path on which such indications occur. The detector device for taxiways and runways may be of the ordinary vehicle detector type designed to close a set of contacts for completion of an electrical circuit upon actuation.

The preferred form of invention includes the use of radar detectors or microwave radiant type detectors that provide a directed beam of microwave radiant energy so that when a vehicle is traveling on the surface or somewhat above the surface of the ground, on the controlled path, detection is made when such vehicle passes through the projected beam and actuates the detector device. Where vehicles are expected to proceed along a relatively conned area, such as a taxi strip or runway, a detector device, such as a microwave radiant energy type detector device, for example, may be used at each detection station where the confined beai'n is directed across such confined area so that an aircraft or other vehicle must pass through such beam while proceeding along such confined area. However, where vehicles are less laterally restricted, such as while airborne in an ascent or descent corridor, multiple detector devices may be used at one detection station where each detector is located on the ground arranged in a line which is perpendicular to the center line of the runway with the confined beam of each detector directed substantially vertically upward so that the joint or aggregate beams combine to form a vertical wall of radiant energy substantially longer than the Width of the runway. Thus an aircraft in such ascent or descent corridor would pass through the radiant energy wall formed by the aggregate beams of the multiple detectors and actuate at least one detector device of the detection stations. Since it is also desired to know the angle of lateral approach of an aircraft, relative to the center line of a runway, indicators individual, to each detector of one detection station having multiple detectors, may be provided to indicate which detector of a multiple detector detection station is actuated, thus indicating the azimuth angle of approach of an ascending or descending aircraft as it passes over and actuates one or more detectors of the detection station in the air corridor.

The relay assemblies, one of which is associated with each detection station, may be identical to each other, and are interconnected identically except for the relay assembly of the first detection station and the relay assembly of the last detection station of a particular series, all as described and illustrated below. Since the relay assembly of the first detection station in a series of detection stations cannot be connected to a forward adjacent unit, a first relay assembly has jumper connections unique to it at its open side. The last or final relay assembly in a series of detection stations which cannot be connected to another relay assembly at its open side also has certain jumper connections which extend off the open end. These end jumper connections also are illustrated and described below.

In its preferred form the display panel of the present invention may be in the form of a layout of the airport runways, adjacent air corridors and taxi strips in miniature, and may have indicator lamps on or next to the miniature layout in positions corresponding to the location of the detector with which the indicators are associated` Each set of indicator lamps may be in a set of three indicators and may be in the form of two arrows,

'each facing in opposite directions along the miniature layout, with a circular or a bar indicator between and below the arrows, forming a third illuminated indicator 'on the panel, associated with one detector.

In the description below, when read with the accompanying drawings, it will be fully disclosed how this present greatly improved traic indicating system or airport surveillance system, through traiiic initiation, trame continuation, and traffic termination accurately indicates the operation of traiiic entering upon, traveling `upon and departing `from the controlled areas of an airport. The present system indicates the point of entrance of Vehicles into the controlled area, indicates the direction of travel of such vehicle, after determination of such direction, its relative velocity or progress, its continued progress along the controlled area, its relative position on the controlled area at all times with respect to the detector last acuated and its exit from the controlled area, all through actuation of the traffic itself and all conveniently displayed on the display panel.

It is therefore an object of the present invention to provide an improved traiiic indicating or surveillance system for an airport or other restricted facilities which is initiated into indication, continually operated and thereafter terminated through actuation of the traffic over which such surveillance is made.

Another object is to provide an improved traic indicating or surveillance system for an airport which will indicate the presence of an aircraft entering into the con- 'trolled area and also indicate the lateral position, with Van aircraft by detectors spaced along such path and automatically setting up the direction of travel progressively on a remotev display panel providing successive indications of the latest detection point passed by the aircraft and for automatically releasing such indications previously set up upon additional actuation of the next .preceding detector along said path. V

A further object is to provide for failure of anyone detection station in an aircraft tracking system without loss of system continuity. y

Another object is to provide a distinctive signal to the traffic director if a vehicle enters an approach zone, runway or taxiway at other than prescribed points.

Another object is to provide a distinctive signal to the traffic director if an aircraft or other vehicle fails to move at normal speed or stops on a runway or a portion of the taxiway where there is normally movement.

It is another object to provide an improved aircraft tracking system including apparatus to indicate when two aircraft that are proceeding in the same direction are traveling too close to one another.

A further object is to provide an aircraft tracking system or apparatus which establishes a preferential direction and indication by initial actuation plus actuation of the adjacent section by an aircraft itself and to .give warning when an aircraft has entered upon and is traveling along the predetermined path in the direction counter to the preferred direction and on a collisionc'ourse with vstrips projecting beams of radiant energy across the same and with additional detectors located olf the ends of the runways, under the air corridors for detection of flying aircraft entering'or leaving the airport;

FIG. 3 illustrates, in perspective view, a desk or work table on the top of which is laid out a miniature of the airport represented in FIG. 2, with lines across the runways and taxi strips located in the approximatepositions of, and corresponding to the detectors placed at the sides of the runways and taxi strips;

FIG. 4, including FIGS. 4a, 4b, 4c, and 4d, illustrates portions of a taxi strip or runway or air corridor on the miniature layout where FIG. 4a illustrates the contour of the several indicators associated with each detection station; FIG. 4b illustrates the indication of one detection station of two arrows illuminated in opposite directions indicating initial detecton of an aircraft and of another detection station of one arrow showing the direction and the approximate position of a second aircraft being tracked on`the same runway or taxi strip; FIG. 4c illustrates that the non-directional detection indicator illustrated in FIG. 4bhas been extinguished and a directional indicator of an adjacent detection station has been illuminated for the same aircraft; with the aircraft ahead proceeding into a new position from that illustrated in FIG. 4b, and FIG. 4d illustrates the indicators that are provided to indicate that two aircraft on the same taxi .strip or runway are on a collision course;

FIG. 5 illustrates in schematic circuit form one complete detection station with a relay assembly, a detector device and output lamps and alarm;

IFIG. 6 represents, in coded circuit form, the extension of the circuits of one relay assembly which may electrically terminate in the adjacent section or the next adjacent section and the circuit modification of the first relay assembly in the series and the circuit modification of the last relay assembly in the series;

FIG. 7 illustrates, in schematic circuit form one form of multi-detector detection station detector indicating apparatus in which the indicator lamps may be switched from one multi-detector detection station detector indicating apparatus to another like apparatus;

FIG. 8 illustrates, in schematic circuit form of circuitry that may be combined with certain of the circuitry of FIG. 7 to combine the functions of the detector indicating lamps and the detection and direction indicating lamps for multi-detector detection stations.

Referring to FIG. l in more detail, part of a runway or taxi strip, TX, is represented with four radiant energy detectors DET1, DETZ, DET9 and DETl represented on the side of the taxi strip, each detector projecting a conned beam of radiant energy across the taxi strip in a fan-like configuration. Each detector is connected to a relay assembly of the interconnected detection stations. The interconnected relay assemblies, RS are represented with relay assemblies RAI, RA2, RA9 and RAl with the relay assemblies arranged in positions relative to each other as the location of their associated detectors, next to the taxi strip, TX. lt should be understood that the space between DETZ and DET9 and between RAZ and RA9 and the panel below represents additional similar units.

Each relay assembly is illustrated with a group of output lines which are connected to a display panel DPL for providing output power to indicators which are located on a miniature layout of the taxi strip TXS with the indicators located in positions corresponding to the location of the detectors on the taxi strip. The indicators Lll, L12 and L13 are controlled by relay assembly RAL indicators L21, L22 and L23 by RAZ, indicators L91, L92 and L93 by RA9 and L10I, LN2 and L193 by RAM?.

The pushbuttons PBI, FB2, PB9 and PBlll represent the manual release pushbutton which are more fully illustrated in the circuit diagram in PlG. 5. An audible alarm, which may be associated with and operated by each relay assembly respectively, is not here illustrated although it may be associated with the display panel, Such audible alarm is illustrated in FIG. 5.

The display panel DPL may be in the form illustrated in FIG. 3 on a desk or table top or other convenient means of providing a layout.

FIG. 2 represents a layout of a typical airport with intersecting runways and a network of connecting taxi strips, a ramp for loading and unloading and a tower. The runways RYl, RYZ and RY3 are normally used for takeoff and landing operations, the runway to be used depending upon the prevailing wind. Along the side of each runway are spaced detectors represented by small Vcircles with fan-like beams extending across the runway.

Along the side of the taxi strips are also located additional detectors represented in similar fashion.

lt will be notiched that the distance between adjacent detectors along the runways and the distance between adjacent detectors along the taxi strip is substantially different. This dierence in distance between adjacent detectors on the runways and adjacent detectors on the taxi strips is determined by the anticipated speed at which the moving aircraft or vehicle may travel. On `the runways a suggested distance between adjacent detectors may be y1000 feet although the distance between adjacent detec- -tors need not be uniform. The suggested distance between adjacent detectors on taxi strips may be 250 feet although small or greater distances between adjacent detectors maybe used in either case, as desired.

Oi the ends of the runway, but substantially in a line perpendicular to a line through the center of the runway,

are located additional detectors. These detectors yare represented by a small solid line circle surrounded by a broken line circle, RDS, for example. These particular detectors are of the radiant energy type detector, the beam of which is projected vertically upward from the ground so that airborne aircraft pass through the vertically projected beam thus actuating the detector.

It will further be noticed that a single detector, for example RDS, at the bottom of runway RYZ is shown at the iirst olf-runway detection station, but at the next detection station out from the end of the runway, three detectors RDSS, are employed, and at the detection station RDSS, the one farthest out, five detectors are spaced to cover a wide air path.

The triangular shaped coniiguration of detectors off the ends of the runway RY2, for example includes three individual detection stations while more or less than three detection stations off the ends of a runway may be used, if desired. The detection stations oft the ends of runway RYB are illustrated with single detectors for convenience.

As an aircraft is about to land, for example on runway RY2, such aircraft may be exactly lined up with the center line of the runway so that such craft will substantially pass over the centrally located detector in the grouped detectors of each detection station. Passage of such aircraft over each detection station will result in, actuation of the detection station itself through actuation of one or more of the particular detectors of the grouped detectors of the detection station and actuation of the multi-detector detection station detector indicating and detection unit which may result in indicating the lateral position of the aircraft with respect to a center line approach to the runway.

Although the grouped detector detection stations are not fully illustrated as being off the ends of all three of the runways, it is obvious that such grouped detector detection stations may be employed olf the end of any one runway, or all runways as desired. Compass directions are illustrated for convenience of illustration.

FIG. 3 illustrates one form of display panel which may be used in the present invention to provide indication of operations on a miniature layout of the airport and adjacent air corridors. The top of a desk, table or cabinet may be used to hold the miniature layout, which desk, table or cabinet may be conveniently adjacent to a work table or other fixture. The lines across the miniature runways and taxiways each represent positions of a detector of a detection station correspondingly located on the side of the actual runway and taxi strip (as in FIG. 2). The line o the ends of the runway represent corresponding positions of detection stations located off the end of the runways.

The triangular configurations on the lower left corner of the desk top and in the lower right corner represent indicator lamps for indicating which one of the grouped detectors of each detection station off the end of the runway was actuated as the aircraft was approaching the runway to land or was in the process of climbing away from the iield. This may indicate the lateral approach of an aircraft to the runway itself.

FIG. 4a illustrates a portion of the miniature layout with the sets of three indicators (two arrows facing in opposite directions, and a circular indicator) at each detection station, shown in broken line form. It is assumed these indicators are not illuminated.

FIG. 4b illustrates a portion of the miniature layout with both arrows Lll and L12 of one detection station illuminated which indication represents detection of a vehicle without any indication of the direction of travel of such vehicle while the single illuminated arrow L31 of the detection station to the right in FlG. 4b indicates that another vehicle or aircraft is in the taxiway and has actuated the detector associated with the detection station of which lamp L3 is a part and is traveling in the direcion of Vthe arrow of indicator lamp L31 along the runway or taxi strip.

' FIG. 4c illustrates that the vehicle or aircraft in FIG. 4b that had been detected and was indicated without a direction (L12 and L11) has actuated an adjacent detector of an adjacent detection station Vand the direction of travel of such vehicle has now been determined and is so indicated by indicator lamp L21 while the vehicle ahead on the taxiway or to the right, has actuated a subsequent detector and iis being tracked as by indicator L41 as it progresses along the runway or taxi strip.

FIG. 4d illustrates the indication provided when two vehicles yare traveling on the same runway or taxi strip in opposite directions and are on a head-on or collision course. Thedirectional indicators L21 and L92 are illuminated to indicate direction of travel and in addition the circular indicator L23 and L93 are illuminated, thus providing an unique combination of signal indication which may be accompanied by an audible alarm, at each position if desired. Y

It should be noted that according to the preferred ern bodiment the non-directional detection indication as shown in for example FIG. 4b by the illumination of LZ and L11 of the same detection station, is shown whenever a vehicle enters upon the controlled path. If the vehicle enters into the controlled path through the first detection station in the series, the non-directional indication is illuminated with steady indicator lamps. If the vehicle enters into the controlled path at any point other than a normal entry station, the preferred embodiment provides a flashing non-directional signal.

The indicators and indications shown here are, of course, illustrative. v

Other types or combinations of indicators or indications may be used by merely connecting the output of the respective relay assemblies in different fashion and to different indicating devices as will be obvious to those skilled in the art using the various known types of indicators.

Referringvnow to FIG. 5, a circuit diagram of the preferred detection station is illustrated with the relay assembly above the broken horizontal line in which the relays are illustrated deenergized and the contacts in their normally deenergized condition. This condition would be the normal rest condition of a relay assembly while awaiting a detection pulse from its associated detector, located below the broken horizontal line.

The detector, normally associated with the relay assembly is represented by a set of open contacts DET surrounded by a broken line box in the lower right of the drawing.

The indicator lamps are represented by open circles labeled No. 1, No. 2 and No. 3 with open circle ALA representing an audible alarm, all below the broken horizontal line. Y

The relay assembly would be duplicated so that each detection station would include an identical relay assembly. The connections between adjacent relay assemblies would likewise be identical, such that the leads of, for example the second relay assembly in a series would connect with the third relay assembly in the series so that the leads through 37 on the right hand side of the second relay assembly would connect with leads 20 through 37 on the left hand side of the third relay assembly and the leads 20 through 37 of the third relay assembly would connection with leads 20 through 37 of the fourth relay assembly, and so forth throughout the series.

There are two departures from the uniform interconnections between relay assemblies with the departures occuring at the terminating ends of the series. Approaching the series of relay assemblies from left to right, the rst relay assembly of the series has its left hand side terminals v20 through 37 which would be open except for a jumper connection between terminals 34' and 37 The terminals on the right hand side of the first relay assembly Z through 37 are connected to the terminals in the left'hand 8 side of the second relay assembly 20' through 37 respectively.

The second departure from the uniform interconnection occurs at the terminals of the last relay assembly in the series at its right hand end terminals. As to the right hand end of the nal relay assembly terminals 20 through 37 will be left open except for terminal 36 which will be connected to a common ground, represented by a minus in a circle.

Thus the several relay assemblies of the series of detection stations may be interconnected so as to provide an interlinking system of identical relay assembly circuits.

Of course each relay assembly circuit will have its associated detector and its individual outputs for operating, holding and releasing the individual indicators and alarms.

The associated detector DET would be positioned so that an aircraft or other vehicle passing through its beam Would actuate the detector which would cause closure of a set ofcontacts thus completing a circuit to energize the detector relay D from a positive direct current supply, represented by a plus in a circle through the coil of relay D, lead 41, the contacts of detector DET, to a common ground represented by a minus in a circle.

Detector relay D substantially initiates the relay assembly circuit into action upon energization and depending upon the condition of the adjacent relay assembly or assemblies, or the next adjacent relay assemblies. The described relay assembly will respond and provide certain output for operation of certain indicators.

The relay D controls contacts D-1, D-2, D-3 and D-4, which are normally open contacts, with contact D-1*c0m pleting the energizing circuit for the ldetector repeater relay DP. Relay DP controls contacts DP-l, DP-2, DP-3, DP-4, DP-5, DP-6, DP-7 and DP-S which are all normally open contacts.

Relay R is a release relay which controls one normally closed contact R-l, through which contact a direct current power source flows for the non-directional relay L and the two directional relays, relay E and relay W. The collision indicator relay C-C' which is a double coil relay also is supplied with power through contact R1. The relay L is a delayed pull-in and delayed drop-out relay while relays Eand W are both delayed drop out relays.

Relay L controls contacts L-l, L-2, L-3, L-4, L-S, L-6 and L7 all of which are normally open contacts. Relay E controls contacts E-l, E-3, E-4, E-5, E-6, E-8 and E-9 all of which are normally open contacts and E-2 and E-7 which are normally closed contacts. Relay W controls contacts W-2, W-3, W-4, W-S, W47, W-8 and W-9 all of which are normally open contacts and W-1 and W-6 which are normally closed contacts. Relay C-C controls normally open contacts C-1, C-2 and C-3.

Relay WP is a repeater relay of relay W and relay EP is a repeater relay of relay E. Relay WP controls normally open contact WP-l and normally closed contact WP-2. Relay EP controls normally closed contact EP-2 and normally open contact `EP-1. The relay WA controls normally open contact WA-l and normally closed contact WA-2 while relay EA controls normally open contact EA-l and normally closed contact EA-2. The relay WJ controls normally open contact WI-l and normally closed contact WI-Z while relay EI controls normallyopen contact EI-l and normally closed contact EI-Z.

Relay T is a time delay relay which upon energization begins to time a period before the relay actually pulls in. Upon pull-in, which may be adjusted as desired up to 10 seconds, for example, the relay T closes normally open contact T-1. The relay F serves as a flasher forcertain of the signalindicators. The relay itself may be Aa self interrupting relay or may have, in its circuit, a flasher, which is well known in the lart. Relay F controls normally closed contact F-1.

Relay R is energized and pulled in by completion of the energizing circuit, normally held open, when push-button PB is manually operated to complete the circuit.

The switch SW1 provides for selection between alternate modes of operation of the collision alarm ALA and indicator lamp No. 3 which are controlled by collision relay C-C. With switch SW1 as illustrated the holding contact C-1 is connected to maintain the collision relay energized as more fully described below.

Switch SW2, illustrated open provides, when closed, a circuit to energize tiasher relay F when the relay L is energized and pulled in. This, as explained below serves to provide a flashing non-directional indication. Switch SW2 may be eliminated and an alternate method of asher operation may be provided by jumper connecting the terminals 4S and 46.

Referring now to FIG. 6 a circuit diagram which represents a series of tive successively spaced relay assemblies is presented with relay assembly RA1, the iirst in the series, and RAS, the last in the series. The relay assembly RA3 is the only relay assembly completely illustrated, although the outputs for operation of the indicators and alarms are omitted.

Through a system of coding it will be seen that the relays of FIG. 5 (the completely illustrated relay assembly circuit of one detection station) appear in relay assembly RAS in FIG. 6 with similar relays lettered with similar letters plus the number of position of the relay assembly in the series. As for example in FIG. 5 relays L, E, W etc. are shown, where in FIG. 6 corresponding relays in relay assembly RAS are numbered L3, E3, W3, etc. In relay assembly RA1 similar relays would be labeled L1, E1 and W1, etc.

Each contact in FIG. 6 is coded so that the letter of the controlling relay appears with a dash followed by a number of the contact which corresponds to a corresponding contact in FIG. 5, as for example, in FIG. 5 the contacts controlled by relay L are numbered L-1, L-Z, L-3, etc. while in FIG. 6 corresponding contacts controlled by relay L3 of RA3 are numbered L3-1, L3-2, L3-3, etc.

In FIG. 6 for convenience of illustration it is assumed that the contacts are all controlled from a relay positioned above the contact and all relays are represented to be deenergized.

It will be noted that certain relay control circuits extend into adjacent relay assemblies and some relay control circuits extended into the next two adjacent relay assemblies. Other relay control circuits are incomplete because of the absence of adjacent relay assemblies.

Referring to the relay assembly RA3, which is an example of a typical relay assembly, the normal pull in circuit for non-directional relay L3 upon a vehicle entry at the boundary detector associated with relay assembly RA3 may be followed from the direct current positive Vpower source, represented by a plus in a circle, through normally closed contact R34 of relay R3, through the coil of relay L3, through contact D13-2, of relay D3, which closed on actuation of the detector associated with RA3, through normally closed contact E3-2, of relay E3, through normally closed contact W31, of relay W3, to common ground. Another closure path for the L3 relay is from contact D3-2, lead 333' to relay assembly RAZ, lead 233, con-tact D23 of relay D2 if closed, to ground or alternatively from contact D3-2, lead 335 to relay assembly RA4, lead 435', contact DP41 if closed, of relay DP-4, to ground.

The holding circuit for relay L3 follows from the power supply through contact R3-1, the coil of relay L3, contact L3-1, lead 334 to RAZ, lead 234, contact WP2-2 of relay WPZ, lead 237 to RA3, lead 337 -to lead 336 to RA4, lead 436 contact EP4-2 of relay EP4 to ground.

The relay L1 in relay assembly RAI has a somewhat modilied holding circuit because of the absence of a relay assembly to the left of RA1. This modied hold circuit for relay L1 includes the elimination of a relay contact of the WP series which would be in the relay assembly to the left, by jumpering the leads 134 and 137. Further, the pull-in circuit for L1 which would 10 include the detector relay contact of the relay assembly to the left of RA1 has been modiiied so as to omit circuitry beyond lead 133.

The relay L5 of relay assembly RAS has a somewhat modified pull-in circuit because of -the absence of a relay assembly to the right of RAS. The relay contacts of the EP series relay to the right of RAS have been eliminated and the lead 535 of RAS, which would connect to contact DP6-1 is open.

The holding circuit of relay L5 in relay assembly RAS is also modified, i.e., the holding circuit of L5 is completed lto ground through a terminal 536 instead of the next EP6-2 relay contact as would be the case if RAS were not a terminating section.

Each relay assembly of each detection station includes a relay of the D series which relay is energized and pulledin upon closure of the associated DET contacts by actuation of the detector. Upon pull-in of relay D the relay DP, a repeater relay of relay D is also energized and pulled-in Contacts controlled by the D relay or the DP relay provide completion of circuitry to energize and pull-in one relay, either relay L or relay E or relay W, depending upon previous history of travel and actuation by the actuating vehicle in the system.

It should be understood that repeater relays are provided to prevent excessively high relay pile up on any one relay. If there were no objection to a high pile up then the contacts of any one repeater relay could be added to the contacts of the relay which controls the respective repeater relay and thus eliminate the repeater relay.

If, for example, there is no previous history by the actuating vehicle regardless where, in the series of detection stations the vehicle enters the system, pull-in of the D series relay and of the repeater relay of the DP series of the same relay assembly by actuation of the associated detector of the detection station will cause energization and pull-in of the associated L series relay. If the vehicle has left a history, as for example, has caused operation of at least one or more prior consecutive detection stations, then, depending on the direction of travel, closure of the contacts of the D series relay or the DP series relay, in cooperation with relay contacts of the last previously operated relay assembly, will energize either the E series relay of the current operated relay assembly (with vehicle traveling from left to right) or the W series relay of the current operated relay assembly (with the vehicle traveling from right to left). The closing of certain of the contacts of the D relay closes an energizing circuit for the associated L series relay, but because of the slow pull-in characteristics of the L relays the relay will not pull-in before pull-in of either the E series relay or the W series relay, both of which may break the energizing circuit of the associated L series relay.

In the preferred embodiment the relay of the L series of each relay assembly is a delayed pull-in and delayed drop out relay with the delay on pull-in of the order of .25 second, for example, and the delay on drop-out of the order of 2 seconds, for example. The relays of the E series and of the W series, in the preferred embodiment are rapid pull-in and delayed drop-out relays, with the delayed drop-out of the order of 2 seconds, for example.

The particular characteristics of the L series, the E series and the W series relays are provided so that although energized, the relay of the L series will only pull-in in the event that neither relay E nor relay W pull in. Pull-in of the relay E and pull-in of the relay W depend on the history of the actuating vehicle in the system and pull-in of the relay L depends upon neither relay E nor relayW pulling in.

Accordingly, in order to pull in relay L3 of relay assembly RA3, relay D3 must be pulled-in to close its Contact D3-2 and both relays E3 and W3 remain deenergized.

As will be seen below, the directional relays of the 11 E series and of the W series of a relay assembly will be energized and pulled in, in the second of two successive relay assemblies upon actuation of two adjacent relay assemblies successively or in the third of three successive relay assemblies upon actuation of the first relay assembly and skipping of the second relay assembly of the series and actuation of the third if the rst of the three relay Aassemblies had already pulled in one of the directional relays. Depending upon the direction of travel from the initially operated relay assembly to the adjacent, 'and subsequently operated relay assembly, the relay of the E series'or the W series of the second successively operated relay assembly will become energized and ull-in.

p The directional relay E3 of RA3, which may respond to a vehicle that is traveling eastbound, for example may be energized via a circuit from the power supply through contact R3-1, the coil of relay E3, contact DP34, lead 330 to relay assembly RAZ, lead 230, contact L2-6 to ground or from lead 230 via contact EPZ-1 to ground or from lead 230, lead 231 to relay assembly RAI, lead 131, contact E11-1 of relay E11 to ground. Upon pull-in of relay E3 relay EP3 becomes energized via closure of contact E3-3 and pulls-in.

The holding circuit for relay E3 may be traced from positive power through contact R3-1, the coil of relay E3, contact E3-1, contact E13-Z, contact DP3-Z to ground or from contact E13-2 lead 332 to relay assembly RA4, lead 432' to contact DP4-3 to ground. Thus in order to energize the relay E3 the relay L2 of RA must be pulled-in or relay EPZ of RAZ (relay EPZ is a repeater relay of E2 of RAZ, therefore relay EZ of RAZ must be pulled-in to energize EPZ) must be pulled-in or relay E11 of RAI must be pulled-in (the relays of the EI series are skip relays that are energized when an E series relay of one relay assembly is pulled-in but the adjacent relay assembly to the right is either missed or fails to respond to actuation and the next to adjacent relay assembly to the right responds to actuations).

Thus, an aircraft or other vehicle traveling from, for example, left to right through the system will, under normal conditions, actuate the initial detector relay, of 'the D series, and cause the L series relay of the initial relay assembly of the initial detection station (relay L1 of RA1) to become energized and pull-in, and, upon the vehicle continuing normally along the pre-determined controlled path, will actuate the'adjacent detector of the de- 'tection station to theright and cause the E relay of the adjacent detection station (relay EZ of RAZ) to become energized and pull-in and cause the L relay of the previous detection station (relay L1 of RA1) to become deenergized and drop-out. As each subsequent detector in the series of detection stations is actuated, its associated relay of the E series will become energized and pull-in `and the `relay of the E series of the adjacent detection station to the left the detection station just previously operated) will be deenergized'and dropped-out.

The E series relay (E1) of the initial detection station in the system (RA1) Will remain deenergized because its energizing circuit is open at lead 130', further, since vRAl is 'the initial detection station'in the system of a left to right series, the system could have no history of the Vactuating vehicle and therefore the relay .ofthe L series (L1) would become energized and pull-in in response to a vehicle irst entering the system atRAl.

The E series relay (E5) of the final Vdetection station in the system (RAS) will become deenergized and VVdrop out upon `deenergization of the associated D series -relay and VDP series relay since the holding circuit which normally has -a .parallel connection to ground through another relay assembly (RA6, not shown) to the right, 'via lead S32, is open.

The directional relay W3 of RA3, which may respond to a vehicle that is traveling westbound, for example'may be energized via a circuit from the power supply through I2 'contact R3-1, the coil of relay W3, contact D3-4, lead 329 to relay assembly RA4, lead 429', contact WP4-1 to ground or from lead 429' `contact L4-'7 to ground or from lead 429', lead 427 to relay assembly RAS, lead S27', contact WIS-'1 to ground. Upon pull-'in of relay W3, relay WPS becomes energized via closure of contact W3-7.

The holding circuit for relay W3 may be traced from positive power through contact R3-1, the coil of relay W3, contact W3 4, contact W13-Z, contact DP3-6 -to ground or from contact W13-'2, lead 328' `to relay assembly RAZ, lead 228, contact yDPZ--S to ground.

Thus in order to energize ythe relay W3 the relay L4 of RA4 must be pulled-in or relay WP4 of RA4 (relay WP4 is a repeater relay of W4 of RA4, therefore relay W4 must be pulled-in to energize WP4) must be pulledin -or relay WJS of RAS must ybe pulled-in (the relay of the WI series being a skip relay that Vis energized when the 'W series relay of one relay assembly is pulled-in but the adjacent relay assembly to the left is either missed or fails to respond to actuation and the next to adjacent relay assembly-tothe left responds to actuation).

Accordinglya vehicle traveling from, for example, right to left through the'systems will, vunder normal conditions actuate the initial detector relay of the D series and cause the L series relay of the initial relay assembly of the initial detection station (relay L5 of RAS) to becomeenergized and pull-in and, upon the vehicle containing normally along the predetermined controlled path, will actuate the adjacent detector of lthe detection station tothe left and cause the W relay of the adjacent detection station (relay W4 of RA4) to become energized and pull-in and cause the L relay Of the previous detection station '(relay L5 of RAS) 'to become deenergized and drop-out. As each subsequent detector in the series of detection stations is actuated, yits associated relay of the W series will become energized vand pull-in and the relay of the W series of the adjacent detection station to the right (the .detection station just previously operated) will be deener- -gized and drop-out.

The W series relay (WS) of the initial detection station in the system (RAS), will remain deenergized because its energizing Vcircuit is open at lead 5529, further -since RAS is the initial `detection `station in the system of a right to left series, the systemcould `have no `history of the-actuating vehicle and therefore the relay ofthe L series (LS) would become yenergized and pull-in in response to a vehicle first entering the system at RAS.

The W series relay (W1) of the final detection station in the system V(RA1) will become deenergized and dropout upon deenergization of the associated D series relay and `DP series relay since the holding circuit which normally has a paralled connection to ground through another relay assembly to the left (RAO, not shown), via lead 128', is open. l

Referring back to FIG. 5 it will be observed tha-t the series L relay controls, among others, contacts L4 and LS which, in series with a normally closed contact YI"-1 of the relay of the F series, close to illuminate the indicator lamps No. 1 and No. 2 respectively. Indicator lamp No. 1 has a parallel illuminating circuit through the series E relay contact E-S and indicator lamp No. Z has a parallel illuminating circuit through the series W relay contacts W-3. Thus when the series L relay of any relay -assembly of a detection station becomes energized and pulls-in, both series indicator lamps No. 1 and No. Z of that detection station will become illuminated. Referring to FIG. 1 and FIG. 4, the indicator lamps L11, LZ1, L91 and L10I are individually comparable to indicator lamp No. 1 in FIG. 5, in their respective detection station while indicator lamps L12, L22, L92 and L102` are individually cornparable to indicator lamp No. Z, in FIG. 5, in their respective detection station.

Accordingly, energization and pull-in of the L series relay will provide illumination of the lamps No. 1 series 13 and No. 2 series and, in the preferred form with both indicator lamps, in the shape of arrows, this indication may mean detection of a vehicle or aircraft but no direction of travel of such actuating vehicle has been established. On the other hand energization and pull-in of the E series relay will provide illumination of the lamp No. 1 series to indicate the vehicle has actuated the associated detector and that it has been established that the actuating vehicle is traveling in the direction of the illuminated arrow, or eastbound for example, while illumination of the ylamp No. 2 series by energization and pull-in of the W relay series may `indicate the vehicle has actuated the associated detector and that it has been established that the actuating vehicle or aircraft is traveling in the direction of the illuminated arrow, or westbound, for example.

Each of the indications, whether of a non-directional nature or of a directional nature indicates the approximate position of the actuating vehicle, relative lto the detector associated with the detection station which has illuminated its indicator.

Referring again to FIG. 6, the EA series relay is energized through the cooperation of the E series relay of the associated relay assembly and the E series relay of the adjacent relay assembly, to the right so that, for example, relay EA3 of RAS will -becorne energized upon pull-in of relay E3 of RA3 plus pull-in of relay E4 0f RA4. The circuit may be traced from a source of power, through contact E3-9, the coil of relay EA3, lead 323 to relay assembly RA4, lead 423', contact E4-8 to ground. Relay EA3 has a holding circuit through its contact EA3-1 to ground. The relay of the EA series therefore, by cooperation of two adjacent relay assemblies may indicate that the relay assembly of which it is a part has responded to an eastbound vehicle and the adjacent relay assembly to the right has also responded tO a preceding actuating vehicle.

The relay of the E1 series operates in coordination with operation of the associated relay of the E series and the associated relay of the EA series and operation of the relay of the DP series in the next-to-adjacent relay assembly to the right.

The energizing circuit for relay E13 may be traced from a source of power through contact E39, the coil of relay E13, contact EA-Z, lead 324 to RA4, lead 424', lead 42S to RAS, lead S25', contact DPS-7 to ground.

Thus, for example, if E3 becomes energized and pullsin through actuation and the actuating vehicle continues to the adjacent detection station to the right and such etection station (relay assembly RA4) fails to respond to actuation, relay E4 of RA4 will not become energized. Thus relay EA3 will not pull-in since contact E4-8 will remain open and with relay EA3 out contact EA3-2 will remain closed. Assuming the actuating vehicle continues on to and actuates the detector of the next adjacent dctection (relay assembly RAS) and relays DS and DPS become energized, the contact DPS-7 will close and complete the energizing circuit for relay E13 of RAS. This is an indication that the detection station of which RA4 is a part, failed to respond to actuation and the next detection station, of which RAS is a part has responded t actuation of the same vehicle.

Certain contacts of relay E13 in RAS control one of the parallel pull-in circuits for the relay E in RAS s0 that the relay ES may become energized and maintain the tracking of the traveling vehicle in the event that one detection station, RA4, for example between RAS and RAS fails to operate in response to an eastbound vehicle.

Further, if, after detection of a vehicle through actuation by the same has been made, a detection station fails to respond to actuation, or the vehicle stops on the predetermined path without actuating the next detection station or the vehicle leaves the predetermined path without actuating either the last detection station or any further interim detection station in the system, the non-direction- 'ifi al relay of the L series, or the directional relay of the E series or the W series of the last actuated detection station will remain energized since the respective holding circuit or" the energized relay will remain unbroken.

In such event a time delay relay of the T series is prO- vided in each relay assembly with three parallel energizing circuits. The circuit of the time delay relay is closed by energization of either the associated L series relay, E series relay or the W series relay; however, the time delay relay is adjusted so as to pull in only after a desired period oi time, as for example ten seconds. If the relay closing the energizing circuit of the time delay relay remains pulled-in for a time exceeding the delay period the time delay relay will pull-in.

For example, the time delay relay T3 of RAS may be energized via a circuit from a source of alternating current power, represented by a plus in a circle in a square, through the coil of relay T3 and through contact E3-4 to common ground or through contact W3-2 to ground or through contact L3-2 to ground.

It the non-directional relay or directional relay then energized and pulled-in remains pulled-in for a period in excess of the delay period so that the time delay relay pulls in, the associated time delay relay of the T series will close its contact T- (re FIG. 5) to complete an energizing circuit for a ashed relay of the F series, which may be a self-interrupting relay, and during its energization the relay of the F series periodically may open and then close its Contact F-l (FIG. 5). The contact F-l is in the circuit for the indicator lamps No. 1 and No. 2 and the lamps No. l and/ or No. 2 will flash on and off.

rThe asher relay of the F series also has a parallel energizing circuit through contact L-3, and through switch Sl/V, or alternatively through jumpered terminals 4S and 46 (FIG. 5), as previously described.

If two or more consecutive detection stations fail to respond to actuation the chain reaction will be broken and the next actuated detection station in the series that respends to actuation of the traveling vehicle will provide a non-directional detection indication, as if entrance had just been made into the system. if this should occur an observer may deduce that either the Vehicle being tracked has followed sorne erratic course or the detection stations that failed to respond are malfunctioning. The indicator lamp of the last actuated station will ilash to call attention to this variation from normal indication.

lt will be noticed that the energizing circuit of relay EAS is incomplete since its energizing circuit is open at lead S23. it will further be noticed that the energizing circuit of relay E15 is incomplete since its energizing circuit is open at lead S24. Further the energizing circuit for relay E14 (not shown) will also be incomplete since its energizing circuit will also be open at lead 52S. Thus although the terminating detection station, RAS, in the left to right direction may be skipped the relay W14 will not pull-in because of a structurally incomplete energizing circuit.

In the event that either the relay of the L series 0r the relay of the E series or the relay of the W series should fail to become deenergized or to be held in because of abnormal operation, a push-button PB (FIG. 5) is provided to manually close an energizing circuit for the associated relay of the R series. When energized, the relay R will open its contact R-1 (FIG. 5) which contact is common to the energizing and holding circuits of the relays L, E, W and C-C of the same detection station so that the relays L, E, W and C-C may be manually deenergized so that a relay that may be held in may be dropped-out and returned to res-t and, with the release of the pushbutton PB, the relay of the R series will drop out and thus the relay assembly Will return to a rest condition.

Referring again to FIG. 6, the WA series relay is energized through cooperation of the W series relay of the associated relay assembly and the W series relay of the adjacent relay assembly, to the left. Thus, for example, relay WAS, of RAS, will become energized upon energization of relay WS of RAS plus energization of relay W2 of RAZ. The circuit may be traced from a source of power through contact W3-8, the coil of relay WAS, lead S', to RAZ, lead 220, contact W29 to ground. Relay WAS also has a holding circuit through its contact WAS-1 to ground. The relay of the WA series therefore, by cooperation of two adjacent relay assemblies indicates that the relay assembly of which it is a part has responded to actuation of a westbound vehicle and the adjacent relay assembly to the left has responded -to actuation of a preceding Westbound vehicle.

The relay of the W1 series operates in cooperation with the associated relay of the W series and the associated relay of the WA series and the relay of the DP series in the next to adjacent relay assembly to the left.

The energizing circuit for lthe relay W13 may be traced from a power supply through contact NS-S, the coil of relay W13, contact WAS-2, lead 321 to RAZ, lead 221, lead 222' to RAI, lead 122 to contact DPl-S to ground.

Thus for example, if W3 of RAS becomes energized and pulls-in through actuation and the actuating vehicle continues to the adjacent detection station to the left and such detection station (relay assembly RAZ) fails to respond to actuation, relay W2 of RAZ will not become energized. Thus relay WAS will not pull-in since contact W2-9 will remain open and with relay WAS out, its Contact WAS-2 will remain closed. Assuming the actuating vehicle continues on and actuates the detector of the next to adjacent detection station (relay assembly RAI) and the relays D1 and DPI become energized and pull-in,

the contact DPI-8 will close and complete the energizing circuit for relay W13 of RAS. This is an indication that the detection station of which RA2 is a part, failed to respond to actuation and the next detection station, of which RAI is a part has responded to actuation by the same vehicle.

Certain contacts of relay W13 in RAS control one of the parallel pull in circuits for the relay W1 in RAI so that the relay W1 may become energized and pull-in and maintain the tracking of the traveling vehicle from right to left in the event that one detection station, RAZ, for example, between RAS and RA1 fails to operate.

It will be noticed that the energizing circuit of relay WAI -is incomplete since its energizing circuit is open at lead 120'. lt will further be noticed that the energizing circuit of relay W11 is incomplete since its energizing circuit is open at lead 121'. Further the energizing circuit for relay W12 (not shown) will also be incomplete since its energizing circuit is also open at lead 122'. Thus although the terminating detection station, RAI, in the right 'to left direction may be skipped the relay W12 will not pull-in because of a structurally incomplete energizing circuit.

In the event that one detection station in the system fails to operate or is skipped the last energized relay of the W series of the E series of the detection station last responding to actuation will remain energized and, as previously described, the associated energized time delay relay ofthe T series will, after the delay period, pull in to close a circuit to energize the associated self-interrupting relay of lthe F series so as to cause the indicator lamp of the last illuminated indicator, before the skipped detection station, to tlash.

Release of the held relay of the W series or the E series may be accomplished manually through closure of the associated relay of the R series by pushing the associated push button PB. Referring to relay assembly RAS, when pushbutton PBS is closed relay R3 is energized and pulled-in. Relay R3 opens its contact R3-1 and opens any energizing or holding circuit of relay LS, E3, W3 or CS-CS that may have been completed.

It will be noticed that each relay ot the E series controls contacts in the energizing circuit of the C relay of the associated double coil relay C-C and that each relay of the W series controls contacts in the energizing circuit of the C relay of the associated double coil relay C-C. The coil C of C-C is connected to the common ground return and the coil C is connected to a direct current positive supply through a Contact of the associated relay of the R series. The interconnecting network of circuits and contacts of the C-C" relays are so arranged so that when a relay of the E series, as for example E2, pulls-in and closes the contact E2-6 and a relay of -the W series, to the right in the system, as for example W4, pulls-in and closes the contact W4-S a circuit is completed to energize double .coil relay C2-C2 and C4-C'4 from positive power through contact R2-1, the coil C2, contact 152-6, lead 226, to RAS, lead 326', contact W3-6, contact E3-7, lead 326, to RA4, lead 426, contact W4-5, coil C4 to ground. Both relays CZ-CZand C4-C4 will become energized and, assuming the switches SW1-2 and SW1-4, not shown, (switch SW1 in FIG. 5) are closed, relay C2-C2 will close i-ts contact C2-1 and contacts C2-2 and C2-3, the latter two contacts shown in FIG. 5, and relay C4-C4 will close its contacts C4-1, C4-2 and Ct-S. Closure of contacts C2-1 and C4-1 will complete holding circuits for relays C2-C2 and C4-C4 respectively.

The manner in which the network of contacts and circuitry of the C-C series relays are connected provides for operation of at least two relays of the C-C Series at one time. In the event that two vehicles enter upon the same controlled path, each traveling in dilerent directions and are on a collision course and the direction of travel of each vehicle is determined, an E series relay on the left end of the system and a W series relay on the right end of the system will become energized and pullin. This combination will provide completion of circuitry to energize and pull-in the C-C relay associated with the energized and pulled-in relay of the E series and also energize and pull-in the C-C relay associated with the energized and pulled-in relay of the W series.

Referring to FIG. 5 it will be seen that the relay C-C controls contacts C-1, C-Z and C-S. Contact C-1 is a holding Contact which, when closed, completes a holding circuit for coil C' through a resistor to ground. The impedance in this resistor may be substantially equal t0 the impedance in the coil C so that as the vehicles progress toward each other and subsequent detection stations track the progress of each vehicle respectively, by re sponding to actuation, closure of, for example, contact N3-5 will open the energizing circuit of the relays C2- C2 and C4C4 but each relay will be held-in via its respective holding contact C2-1 and C4-1 and the total impedance in the holding circuit will be substantially equal to the total impedance in the pull-in circuit.

Thus, with the switch SW1 of all relay assemblies closed, the collision indication of each detection station that has responded to the collision course of travel will be held operated, until released by operation of each respective pushbutton PB, which will operate the respective Y relay ofthe R series to reset the relay assembly.

Alternately, with switch SW1 open, the holding circuit of the C-C relay will not he completed and only the C-C relays of the then responding detection station will be operatedto operate its associated collision alarm.

As with the tracking in the eastbound direction, if two or more consecutive detection stations fail to respond to actuation of a westbound vehicle, the chain reaction of the interconnected relay assemblies will be broken and the next actuated detection station in the series that responds to actuation of the traveling vehicle will provide a non-directional detection indication.

Referring now to FIG. 7 lthe multi-detector detection station detector indicating device is represented in circuit form. This detector indicating device includes circuitry for indicating which one of tive detectors vof a live detec- 17 tor detection station has been actuated by a flying aircraft and also provides a pulse to the detector relay of the relay assembly of the detection station upon actuation of one or more of the detectors.

Although a tive unit indicating device is illustrated obvious an indicating device including more than ve units or less than live units may be made by, for example, adding one or more units such as that enclosed in the broken line box 701 or eliminating one or more such units and closing the circuit accordingly.

It should be understood that the multi-detector detection station detector indicating apparatus may be employed to indicate which one or more detectors of a multidetector detection station are actuated by a dying aircraft. This last indication may be in addition to the described directional indicators which may be located on the panel at positions relative to the position of the detection station.

However, as more fully described below and illustrated in FIG. 8, these two last mentioned functions may be combined so as to indicate which one or more of the detectors of a multi-detector detection station are actuated and at the same time provide a directional indication of the actuating aircraft. This latter or combined function method would provide for the placement of the multiple combined indicators, which may indicate detection and direction as well as the position of the detector or detectors actuated, at a position on the lay-out, relative to the location of the detector to which the indicators respond.

Referring to FIG. 7, let it be assumed that the multidetector detection station detector indicating apparatus is used in addition to the directional indicators operated by the relay assembly of the associated detection station.

Let it further be assumed that the five open contacts RDS-1, REE-2, RDS-3, RDS-4 and RDS-S represent the radiant detectors of a tive detector detection station, as for example the tive detectors of the multi-detector detection station off the end of the south end of runway RY2 and generally labeled RDSS in FG. 2 and further assume that the indicator lamps DLS-l, DLS-2, DLS-3, DLS-4- and DLS-5 represent the indicator lamps generally labeled DLS on the left side of the panel of the miniature lay-out panel in FIG. 3.

Geographically the detectors of a multi-detector detection station may be located on the ground, in a line which is perpendicular to the center line of the runway with the middle detector (detector RDS-3) on the line with the center of the runway and the other detectors olf to the left and to the right of the center line of the runway, respectively. The detectors of the multi-detector detection station may be spaced some 250 feet apart, for exarnple, and the ultra high frequency radio energy beam of each detector may be projected into the air, perpendicular to the center line of the landing runway, and may be joined together to form a wall of radiant energy, so that an airborne aircraft on its landing approach or its take-olf leg may pass through this radiant energy wall so as to actuate one or more of the detectors and thus actuate the detection station of which the detectors are a part.

It should be understood that one or more detectors of a multi-detector detection station may be actuated by an aircraft dying through this wall of radiant energy according to the size of the aircraft, its altitude and its position relative to the detectors.

Let it further be assumed that an aircraft, in its landing approach, for example, approaches the landing runway RYE from the south, passes through the wall of radiant energy and actuates one of the detectors of the RDSS group of FIG. 2, for example, the detector represented by RDS-3 of FIG. 7.

Actuation of the detector represented by RDS-3 will cause closure of the normally open contacts RDS-3 to complete a circuit from ground through contacts RDS-3,

. i3 the coil of relay DDS to a power supply. Energized relay DB3 will close its contacts 702, 733, 704 and 765.

Closure of contact 7%2 will complete a holding circuit for relay DDS from a power supply through the coil of relay DD3, contact 762, lead 7%, selector switch SW?, Contact 7%9 of thermal delay relay 710 to ground. Closure of contact 763 completes a circuit to heat the heater coil of thermal delay relay 71@ from a power supply through heater coil 712, lead 73, contact 763 to ground. The use of selector switch SW9 will be discussed below.

Closure of contact 7Std completes a circuit to energize relay PR and the detector relay, relay D, FIG. 5 of the relay assembly of the multiple detector detection station. The circuit for energizing relay PR may be traced from a power supply through the coil of relay PR, lead 7l4, contact 764 to ground.

Relay PR may be a slow pull-in type relay so that the circuit for energizing the detector relay (relay D in FIG. 5) in the relay assembly of the detection station is completed for a finite period as determined by the time between energization of the coil of relay PR and actual pull in causing the opening of contacts 76. The circuit to energize the detector relay of the associated relay assembly may be traced from ground through contact 7%4, lead '714, diode '/It, contact 7i() of relay PR. The lead extending from contact 715 is connected to the lead fil in FG. 5 which is connected to lead 41 of FG. 5 and thence to the coil of relay D and thence to a positive supply. The detector DET, in FIG. 5 may be disconnected for any detection station in which the assembiy in PEG. 7 is employed. After completion of the pull-in circuit for the detector relay, the relay PR may pull in and open its contact 716 to ensure against multiple pulses to the detector relay of the associated relay assembly.

Closure of contact 7th? completes an illuminating circuit for the indicator lamp DLS-3, which is representative of one of the grouped indicator lamps DLS in FIG. 3, and is in a comparable position in the line of indicator lamps DLS illustrated on the lay-out in FIG. 3. The indicator lamp DLS-3 is also in a position comparable to the detector RDS-3, relative to the group RDSS. The illuminating circuit for DLE-3 may be traced from ground through contact 705, lead 719, to the full clockwise position of selector switch SWS, the arm of selector switch SWS, lam-p DLS-3 to a power supply.

It should also be understood that completion of the energizing circuit of the detector relay of the relay assembly operates the relay assembly of the detection station the same as if the detector DET of FlG. 5 had closed its contacts to energize the detector relay. Also the directional indicator lamps, represented by No. 1 and No. 2, of that particular detection station may also be illuminated depending upon previous actuation of adjacent or next to adjacent detection stations and the direction of travel of the actuating aircraft.

V-fith selector switch SWS* in its center position, as illustrated, the holding circuit for the relay DB3 includes contact 769 of the thermal delay relay 710.

Thermal delay relay 7i@ will hold its contact 769 closed until `the heater coil 71?. heats up enough to open contact 7d?, at which time the holding circuit for relay DB3 will open at contact 709 and the relay DDS will become deenergized and release its contacts (so long as actuation of the detector has ceased) thereby deenergizing relay PR and extinguishing indicator lamp DLS-3. The time delay on the opening of contact 709 may be of the order of 20 seconds, for example.

Thus, through illumination of one or more (depending upon the wing span and position of the aircraft as it passes through the radiant energy wall over the detectors) of the indicator lamps the approximate lateral angle of approach of the actuating aircraft may be determined, relative to the center line of the landing runway.

Each of the multi-detector detection station would have I9 its own detector indicating apparatus with as many units, such as unit 791, as there are detectors in the lmultidetector `detection station.

The indicator lamps of the arrangement illustrated in FIG. 7 may be positioned on the miniature layout panel at the ends of the associated runway and in positions relative to the geographical location of the detector to which it will respond or may be positioned as illustrated in FIG. 3. Other indicators such as indicators No. 1, No. 2 and No. 3 of FIG. 5, for each detection station may be positioned on the miniature layout in positions relative to the position of the grouped detectors of the `detection Istation so as to indicate detection of an actuating aircraft and/or direction of travel of such aircraft, along with the detector indicator lamps.

However, it is not unusual practice to use one runway for landing and another runway for take-off, but more often than not, the runway used for take-off and landing is the same runway, yand it may be desired to use two triangular indicator lamps configurations, in lieu of a triangular indicator conguration at the end of each runway. As indicated in FIG. 3, two such triangular indicator configurations may lbe used with the triangular indicator lamp configurations switched to the runway then inuse.

Along these lines switch SWS represents one method of switching one group of detector indicating lamps between certain of the runways.

The ganged switch SWS may be used to select between the south end of runway RYZ (leads RYZS), the west end of runway RYI (leads RYIW) or the northwest end of runway RYS (lead RYSNW) by the positions of the ganged yswitch arms of switch SWS.

With the ganged Aswitch arms in the full clockwise position, all the indicator lamps would rbe connected to the detector indicating illumination circuits for the south end of runway RYZ through leads RYZS, so that the indicator lamps DLS-I, DLS-2, DLS-3, DLS-4 and DLS-5 may represent the grouped detector RDSS. In fthe center position the arms of switch SWS may connect the indicator lamps to the detector indicating illumination circuits for the west end of runway RYl through leads RYIW Afor example, so that the indicators lamps DIS-1, DLS-2, etc., may represent the five detectors RDSW, not shown. The lead RYENW in the full counterclockwise position would connect to the detector indicating illumination circuit for the northwest end of runway RYB so that the indicator lamps DLS-1, DLS-2, etc., may represent the live detectors RDSNW, not fully shown.

Obviously each group of indicators in the same triangular configuration would be switched to the comparable detection stations off the end of the same runway.

Thus with two triangular grouped configuration indicator lamps, both the landing aircraft and the departing aircraft may be indicated with the grouped configuration indicator lamps switched, as desired, to connect with the detector indicating unit of the detection stations olf the ends of the runway or runways then in use.

The selector switch SW9 provides for various modes of controlling the holding circuit of the energized one or more relays (DDI, DDZ, etc.) upon actuation of the associated detector, and thus controlling the length of time of illumination of the detector indicator lamps.

The selector switch SW9 may be positioned in its full counterclockwise position so that the respective holding circuits of the respective relays DDI, DDZ, DDS, DD4 and DDS are open and the relays will not hold in after actuation has ceased, as previously described.

This provides for actuation of the detector, or detectors, energization of the associated relay, or relays, energization of the PR relay and illumination of the detector indicator lamp or lamps during actuation only or during the time the aircraft is physically passing through the projected beam or beams.

The length of time actuation may occur depends upon the size and speed of the aircraft and the width of the projected beam at the altitude at which the aircraft passes through the beam.

With the selector switch SW9 in its full clockwise position the holding circuits of the respective relays DDI, DDZ, etc., may be controlled by the non-directional (L), or one of the directional (E or W) relays in the associated relay assembly of the detection station. As illusltrated the terminal of the full clockwise position of switch SW9 continues out lead 42', which may be the lead 42 in FIG. 5.

As previously described, when the multi-detector detection station detector indicating apparatus is employed as part of a multi-detector detection station the energizing circuit for the detector relay of the associated relay assembly is completed through a circuit controlled by one or more of the relays DDI, DD2, etc. Energ-ization of the detector relay (relay D of FIG. 5) of the associated relay assembly provides for operation of the relay assembly, the same as `if the detector relay of the relay assembly would have been energized in response to closure of the contacts DET, shown in FIG. 5.

As more fully described with reference to FIG. 5 when the relay assembly operates one of the relays L, E or W will become energized and close respectively controlled contacts, including contact L-2, E-4 or W`2 respectively. Referring to FIG. 5, it may be seen that upon closure of any one of these last named contacts ground or negative power, will be applied through the closed contact and to the lead 42. Since the lead 42 in FIG. 5 is assumed to 'oe the lead 42 in FIG. 7 then ground would be supplied via lead 42 in FIG. 5 4to the full clockwise position terminal of switch SW9 in FIG. 7 to the moving element of switch SW9 and then through the closed holding contact of the relay then energized, so that the holding circuit for lthe respective relays DDI, DB2, etc., through positioning the arm of switch SW9 in its full clockwise position, may be controlled via the non-directional or one of the directional relays (L, E or W) of the relay assembly.

Thus with the holding circuits of the relays DDL DB2, etc. of FIG. 7 controlled and held as long as the nondirectional or one of the directional (L, E or W) relay of FIG. 5 remain pulled-in, the detector indicating indicator lamps may be illuminated and held illuminated for substantially the same period as the detection and direction indicating lamps No. 1 and No. 2 of FIG. 5, also controlled by the relay L, E and W as described.

It may be desired to combine the function of the detector indicator lamps such as DLS-1, DLS-2, etc., and the detection and direction indicator lamps, such as No. 1 and No. 2 of the same multi-detector detection station.

In this direction FIG. 8 is presented as part of one method and circuitry which may accomplish such end.

Referring to FIG. 5, it Will be noticed that a lead 43 extends from the illuminating circuit of indicator lamp No. 2 and a lead 44 extends from the illuminating circuit of indicator lamp No. 1. The leads 43 and 44 of FIG. 5 may represent the leads 43 and 44 respectively of FIG. 8.

It will be noticed that the coils of the relays L, E, W and F appear in phantom form in FIG. 8 and represent the relays L, E, W and F respectively of FIG. 5. The circuitry under the relays with the numbered contacts represents similar circuitry and contacts similarly labeled in FIG. 5. i

The coils of the relays DDI, DDZ, DB3, DB4 and DDS are alsoillustrated in phantom form in FIG. 8 and represent the relays similarly labeled in FIG. 7.

By combining the functions of the multi-detector `detection station detector indicating apparatus and the circuitry for providing detection and direction indication,

indicators may be provided to indicate which one ork more detectors of a multi-detector detection station are 21 actuated and, at the same time indicate that there has not yet been a direction or" travel established, or if such direction of travel has been established, and indicate such direction of travel of an actuating aircraft.

To provide circuitry and apparatus to combine the indicator functions as mentioned above, the indicator illuminating circuitry and components illustrated in FIG. 7 below the broken line 7-8 would be removed and would be replaced by the circuitry and components illustrated in FIG. 8 below the broken line 7 3 in FIG. 8. The leads 43 and 44 or" FIG. 8 would connect to the leads 43 and 44 respectively of FIG. 5, or as previously suggested the leads 43' and 4d may be considered to be the leads 43 and 44 respectively in FIG. 5 and in such manner the circuitry of the several figures may be connected along with the connection to lead 41 and through lead 42.

lVith such combination the preferred position of selector switch SW9 is ull clockwise so that the holding circuits of the relays DDI, DDZ, etc. are controlled by the relay assembly through contacts of relays L, E or W.

As in FIG. 7 above, ve indicator units are illustrated, however more than ve or less than iive indicator units may be provided, similar to the indicator block orf by broken line 701', for example the same as described with reference to FIG. 7, according to the number of detectors in the multi-detector detection station.

Associated with each of the relays DDI, DDE., DB3, DB4 and DDS are a set of two indicator lamps. Each lamp of the set of indicator lamps associated with one of the relays DDI, DDZ, etc., and thus associated with one of the detectors of the multi-detector detection station is provided with an arrow to indicate opposite directions so that direction of travel of the actuating aircraft may be indicated as well as its transverse position relative to the center line of the runway.

Each set of two indicator lamps, LW and LE, for example, such as the indicator lamps surrounded by the broken line box 731, in FIG. 8, may be positioned on the miniature lay-out relative to the location of its associated detector and with the arrows of each lamp of one set pointing in opposite directions of travel of an aircraft.

Thus with multiple multi-detector detection stations located off the end of a runway, such as off the south end of runway RYZ in FIG. 2, for example, a triangular configuration of indicator lamps would appear oft the end of the runway or runways in lieu of at the sides of the indicator panel, as indicated in FIG. 3, for example.

Also associated with each group of sets of two indicator lamps of a multi-detector detection station would be an indicator larnp, such as LL3, in FIG. 8, which represents the indicator lamp No. 3 in FIG. 5.

Referring to FIG. 4a, and in particular the indicator lamps L12, L11 and LI3, the set of lamps LIZ (LW in FIG. 8) and L11 (LE in FIG. 8) would be duplicated for each detector of the multi-detector detection station but only one lamp L13 would appear for each detection station regardless of the number of detectors associated with the multi-detector detection station.

As seen in the circuitry in FIG. 8, it will be appreciated that either `indicator LW' or LE of the set 731, for example, or both lamps LW and LE may be illuminated depending upon which relay L, E or W, of the relay assembly is energized, assuming of course that the detector associated with the relay DD3 is actuated.

Thus, assuming now that the circuitry below the broken line 7 3 of FIG. 8 has replaced the circuitry below the broken line 7 8 of FIG. 7 and that the leads 43' and 44 of FIG. 8 are connected to the leads 43 and 44 of FIG. respectively and the switch SIF/'9 is in its full clock-- wise position, further assume that an aircraft passes through the radiant energy wall and actuates one of the detectors, for example RDS-3, of the multi-detector detection station.

Closure of RDS-3 completes a circuit to energize relay DD3 of FIG. 7, as previously described.

Energized relay DD3 will close its contacts 702,703, '71% (of FIG. 7) and 732 and 733 (of FIG. 8).

Closure of contact 7% completes an energizing circuit for the detector relay (D) in the relay assembly, FIG. 5, from ground in FIG. 7 through contact 704, lead 714, diode 715, contact 716, to the lead connected to lead 41 in FIG. 5, lead 41, the coil of relay D to a positive power supply.

Energized relay D of FIG. 5 Will close its contacts to pull-in relay DP, which will close its contacts.

Now, as described herein relative to FIGS. 5 and 6, either relay L or relay W or relay E will become energized and pull-in.

Assuming that relay L of FIG. 5 pulls-in, the relay L will close its contacts, including contacts L-5 and L-4 and both indicator lamps LW and LE of 731 (FIG. 8) will become illuminated. The circuit may be traced from a positive supply in FIG. 5 (also shown in FIG. 8), through contact F-I of relay F, contact L-4 of relay L, lead d4, (which is lead 44 in FIG. 8), contact 733 of relay DD3 lamp LE to ground and from the positive supply in FIG. 5 (also shown in FIG. 8) through contact F-I, contact L-S of relay L, lead 43, (which is lead 43 in FIG. 8) contact 732 of relay DD3 to lamp LW to ground, thus illuminating the set of indicator lamps 73I in FIG. 8.

The relay L of FIG. 5 will also close its contacts L-2 (in FIG. 5) and complete a holding circuit for relay DD3 from a positive supply in FIG. 7 through the coil of relay DD3, Contact 702, lead 7 @5, the arm of switch SW9, in its full clockwise position lead 4Z which connects to lead 42 in FIG. 5, contact L-2 to ground.

Relay DB3 will cause relay PR to pull-in and thereupon relay PR will open its Contact 716 to open the detector relay (D in FIG. 5) energizing circuit.

Now the relay DDS, for example, will hold in so long as relay L of the associated relay assembly is held-in, thus cooperating to maintain the indicator lamps LW and LE illuminated so long as both relays DD3 and L are heldin.

Assume now that the relay E of the relay assembly of FIG. 5 pulls-in. The relay E will close its contacts to complete a circuit to illuminate indicator lamp LE of 731 from positive power (in FIG. 5,) contact F-I, contact E-S, lead 44 (or lead 44'), contact 733, lamp LE to ground.

Closure of contact E-d and thence lead 42 in FIG. 5 will complete the holding circuit for relay DDS in FIG. 7.

Thus relay DDS will be held-in by contacts of relay E and the lamp LE will be maintained illuminated through cooperation of relay DD3 in FIG. 7 and relay E in FIG. 5.

If it be assumed that the relay W were pulled in lieu of relay L or relay E then the contact W-Z (in FIG. 5) will complete the holding circuit via lead 42 in FIG. 5 and closure of contact W-3 will complete an illuminating circuit for indicator lamp LW of 731 in FIG. 8. Positive power from FIG. 5 may be applied via contact F-1, contact VJ-3, lead 43 (lead 43' in FIG. 8), contact 732, lamp LW to ground.

Thus cooperation of the relay DD3 in FIG. 7 and relay W in FIG. 5 may maintain illumination of lamp LW in FIG. 8.

The lamp LL3 of FIG. 8, which represents the lamp No. 3 in FIG. 5 will be illuminated as described with reference to FIG. 5 and FIG. 6.

It should be noted that if two detectors of any row of detectors of a multi-detector detection station are actuated, as for example the detectors RD5-2 and RDS-3 represented in FIG. 7, one or both of the indicator lamps LW and LE of block 731, of FIG. 8, controlled by relay DDS and relay E, W or L, may be illuminated along with the corresponding lamp or lamps of the set of indicators 735 which is similarly controlled by the relay DDZ through actuation of RDS-2.

Referring again to FIG. 8, the arrows of the lamps of the several sets of indicators are shown all pointing horizontally for convenience of illustration. It will be understood that each set of two indicator lamps, when positioned on a miniature layout or panel, in a row of sets of indicator lamps corresponding to the row of detectors of one multi-detector detection station would have the arrows of the individual lamps of the same set pointing in opposite directions along the normal travel path with corresponding lamps of the different sets pointing in the same direction. Thus the arrows would be pointing perpendicular to the row of indicators, instead of pointing in line with the row as shown in FIG. 8.

Thus a group of sets of indicator lamps may be positioned on a panel or lay-out, transverse to the center line of the lay-out of the runway, each set of indicators in a position corresponding to the position of an associated detector of a row of detectors of a multi-detector detection station located oif the end of the runway and transverse to the center lineV of the runway so that when any one or more detectors of the row of detectors ar actuated by a passing aircraft one or both lamps of a set of indicators associated with the detector or detectors actuated by the passing aircraft may be illuminated and may indicate the direction of travel of the actuating aircraft along its path and the transverse position of the aircraft with respect to the center line of the runway, the direction indication depending on prior actuation of a detector in a preceding7 row representing a preceding de-Y tection station.

It has been described how the relay circuitry of certain of the relays of one relay assembly extends into certain of the other relay assemblies in a series of multiple relay assemblies of multiple detection stations. It

should be understood that although FG. l represents a system including ten detection stations, four of which are illustrated, in block form, and FIG. 6 shows tive relay assemblies, one of which is fully illustrated, except for the outputs, in a system, any number of 'detection stations, similar to that illustrated in FIG. 5, may be com` bined in series connection of their respective relay assemblies to form a trafiic surveillance system. The rnumber of detection stations in one complete system will depend upon the length of the predetermined path to be controlled and the distance between each detector of the respective detection station. It should further be understood that the distance between detectors of one complete system need not be uniform.

It has also been described how the extreme end relay assemblies are jumpered on certain of their leads to form initiating and terminating relay assemblies of the system. Each end detection station may serve as an initiating and terminating detection station, depending on the direction of travel of the actuating vehicle throughout the system.

It will further be noticed that the system presented herein has no predetermined or pre-established direction of preferential travel, that such preferential direction is determined within the system itself upon detection of a vehicle and subsequent determination of direction of travel of such vehicle.

The traiiic surveillance system is designed to permit indicated tracking of vehicles in both directions along the predetermined controlled path with an unique warning and indication when two Vehicles are traveling on the same predetermined path and are on a head-on or colli-v sion course as well as other indication of travel patterns of vehicles.

Let it be assumed that a traic indicating system includes tive detection stations and that with the trac indicating system at rest a vehicle approaches the rst in a series of five detectors of the respective detection station. Using `the FIGS. and 6, that is FIG. 5 to illustrate the complete detection station and FIG. 6 to illus- Z4 trate some of the extensions of the circuitry of the relay assemblies, the relay operation of the responding detection stations will be described.

As the vehicle, which may be a surface vehicle or an aircraft, traveling from left to right, enters the radiant energy beam of the first detector DETI, the detector will be actuated and close its contacts (included in DETI). The detector relay D1 of RAl is energized by the circuit completed by closed contacts DETI. Relay D1 pulls-in and operates its several contacts and completes a circuit to energize and pull-in detector repeater relay DPl via contact Dil-1. The energizing circuit for relay L1 is also completed from positive power through contacts R14, the coil of relay L1, D1-2, E12 and W1-1 to ground. The energizing circuit for relay E1 is open since lead 136', extending to the left hand side of RAI, is open. The energizing circuit for relay W1 is open at contacts WP21 of RAZ, L2f-7 of RAZ and W13-1 of RAS.

After a short delay relay L1 pulls in and closes contacts so that the non-directional indicator indication (lamps L11 and L12 as in FIG. 4b) is illuminated and time delay relay T1 is energized but does not pull-in. It

is assumed that the switch SW2 in RA1 is open so that' the lamps L11 and L12 are heldV illuminated and not dashed.

Energized relay L1 also closes a holding circuit from positive power via contacts R1-1, L1-1, lead 134', a jumper connection to lead .137', lead 136 to RAZ, lead 236 and contact EPZ-Z to ground.

If another vehicle had just preceded the assumed vehicle and this second vehicle was simultaneously actuating the second detection station of which RAZ is a part the pull-in circuit for relay L1 of RAI may be completed from the contact Dlt-Z through lead to RAZ, lead 23S', contact BP2-1 of relay DPZ of MZ to a ground connection.

f When the irst assumed vehicle passes out of the radiant energy beam actuation of the detector DETI will cease and contacts DETI will open causing relay D1 to drop out. With relay D1 deenergized, relay DP1 becomes deenergized and drops out. Contact D1-Z opens to open the pull-in circuit of relay L1.

Relay L1 holds through its holding circuit and maintains illumination of indicator lamps L11 and L12 and energization of delay relay T1, which relay will not pullin until the end of its delay period.

As the rst assumed vehicle proceeds to the right or to the east, for example, it will enter into the radiant energy beam of detector DETZ of the next detection station. Relay DZ of RAZ will become energized and pull-Y in upon closure of contacts DETZ. Relay DPZ will become energized and pull-in through closure of contact DZ-l.

Closure of contact DZ-Z completes an energizing circuit for relay LZ va contacts RZ-l, DZf-Z, EZ-Z and WZ-l and closure of contact BP2-4 completes an energizing circuit for relay E2 (not shown) from a power supply via contact RZ-l, the coil of relay EZ, Contact BP2-4, lead Z39 to RA1, lead 13? and Contact L1-6 to ground. Relay EZ pulls-in immediately. The energizing circuit of relay LZ is also closed as described, but relay LZ is a delay-on-pull-inrelay and its energizing circuit is opened by the rapid pull-in of relay E2,v opening its contact EZ-Z. Thus relay L2 does not pull-in.

Energized relay FZ closes its contacts to energize and pull-in relay EPZ, via contact EZ-3 and to illuminate indicator lamp L21 (as in FIG. 4c), via contact EZ-S (contact E-S of FIG. 5) and to energize time delay relay TZ, Via contact EZ4. Relay EZ also closes contact EZ-7 in the energizing circuit of coil C'Z of CZ-CZ but the energizing circuit is open at other contacts in the other relay assemblies to the right and relay CZ-CZ re-V mains deenergized,

Relay EZ closes contact EZ-l which completes a holding circuit from positive power via contact RZ-l, the

25 coil of relay E2, contacts EZ-l, E12-2 and DEZ-2 to ground and also an alternate holding circuit from contact E12-2 lead 232 to RAB, lead 332', contact DPS-3 to ground.

The circuitry and contacts controlling and controlled by relay E2 (not shown) of RA2, are identical in structure to the circuitry and contacts controlling and controlled by relay E3 of RA3.

When relay EPZ (not shown) becomes energized it opens its contact BP2-2 and opens the holding circuit of relay L1. Relay L1 is delayed on drop-out as Well as on pull-in so that relay L1 becomes deenergized but holds in for a short time, of the order of 2 seconds, for example. Thus at this time indicator lamps L11 and L12 of RAI and indicator lamp L21 of RAZ are all illuminated.

After the short delay relay L1 drops out and extinguishes the lamps L11 and L12 and deenergizes relay T1 which had not pulled in since it is here assumed that the delay time of relay T1 has not been exceeded. Contact L1-6 is also opened to open the puli-in circuit for relay E2. Relay E2 holds-in via its holding circuit through contacts R21, E2-1, E12-2, leads 232 and 332 to contact DP3-3 to ground.

With the drop-out of relay L1 and extinguishing of indicator lamps L11 and L12 and the deenergization of relay T1 the relay assembly RAl returns to a rest condition.

Relay E2 also closes its contact E2-9, (not shown) which prepares a pull-in circuit for relay EA2, (not shown).

When the actuating vehicle passes out of the beam of DETZ actuation ceases and relay D2 drops-out thereby dropping out relay BP2. Relay E2 holds pulled-in and maintains indicator lamp L21 illuminated and relay EPE energized and pulled-in and relay T2 energized but not pulled-in.

Upon actuation of DETS of the next detection station, of which relay assembly RA3 is a part, relay D3 pulls-in via closure of contact DET3. Relay D3 closes contact D3-1 causing relay DPS to pull-in. Relay L3 is energized but does not pull-in, the energizing circuit including contacts R3-l, D3-2, E3-2 and W3-1. Relay E3 is energized and pulls-in to break the energizing circuit for relay L3 at contact E3-2.

Relay DPS opens its contact DP3-3 which breaks the holding circuit for relay E2 of RAZ. Relay E2 is delayed on drop-out and holds in for a short time, of the order of 2 seconds, for example While the pull-in circuit for E3 is completed from positive power through contact R3-1, the coil of relay E3, contact DP3-4, lead 330 to RAZ, lead 230 and contact EPZ-1 to ground. Relay E3 closes its holding circuit which may be traced from positive power through contact R3-1, the coil of relay E3, contacts EIS-2 and DPS-2 to ground and from E13-2, lead 332 to RA4, lead 432', Contact DP4-3 to ground.

Relay E3 closes contacts to illuminate indicator lamp L31, and energize time delay relay T3 and closes its contact E3-8 to complete the prepared energizing circuit for relay EA2 in RAZ, from positive power via contacts E2-9, the coil of relay EAZ, lead 223 to RA3, lead 323', Contact ES-S to ground. At this time indicator lamps L21 and L31 are both illuminated, and since both relays E2 and E3 are held in relay EAZ of RAZ is energized and pulled via contacts Eil-9 and E3-3.

Relay E2 drops out followed by relay EPZ of RAZ, and the lamp L21 is extinguished. The energizing circuit for time delay relay T2 is also opened, relay T2 not having pulled-in. Relay EAZ is also dropped out when E2 drops-out.

When the vehicle proceeds out of the detector beam, actuation of detector DETS ceases and relay D3 and DP3 drop out leaving relays E3, EP3 and T3 energized but with relay T3 not pulled in. L31 remains illuminated.

Let it now be assumed that the vehicle stops before entering the beam of the next detector or travels very slowly that the delay period of time delay relay T3 expires and relay T3 pulls in. VJhen relay T3 pulls-in the relay F3 becomes energized via contact T3-1 and relay F3, being a self-interrupting relay, successively opens and then closes contact FE1-1 (F-l in FIG. 5) in the illuminating circuit for lamp L31 so that the indicator lamp flashes on and ol. This reaction will occur if any vehicle over stays the timed delay period of the associated T series relay.

T nen the vehicle moves into the beam of DET4 so as to energize and pull-in relays D4 and DP4, relay L4 will become energized and relay E4 will become energized and pull-in. The energizing circuit of relay L4 will become open at contact E4-2 and relay EP4 will become energized and pull-in via contact E4-3. Indicator lamp L41 will become illuminated and relay T4 will become energized. The holding circuit of relay E3 will be opened at contact DP4-3 but relay E3 holds in for its delayed drop-out period.

Relay EAS will become energized and pull-in from positive power through Contact E39, the coil or relay EA3, lead 323 to RA4, lead 423', contact ,E4-8 to ground. Assuming lamp L31 had been hashing this would leave indicator lamp L3 ashing and lamp L41 illuminated steady. The energizing circuits for relays E4 and EP4 are similar to the structure of the energizing circuits for relays E3 and EP3 respectively.

Subsequent drop-out of relays E3 and EP3 Will cause deenergization and drop-out of relay T3 which dropsout relay F3 While relay E3 extinguishes indicator lamp L31 and causes relay EA3 to drop-out.

lf the vehicle should exit from the beam of DET4 so that relay D4 and relay DP4 are dropped-out and should then leave the predetermined path Without passing through any subsequent detector beams in the series, so as to fail to operate the next detection station, as for example, if relay assembly RA4 is operated, as described and the Vehicle leaves the path Without operating relay assembly RAS due to its failure to actuate detector DETS, or the relay assembly RAS fails to respond to actuation of detector DETS, then relay E4 will hold-in due to its holding circuit not being opened at contact DPS-3. The indicator lamp L41 Will, after expiration of the delayed period of relay T4, begin to flash due to relay T4 being pulled-in and its pulling-in relay F4.

In order to return the relay assembly RA4 to rest, pushbutton PE4 may be manually pushed closed to complete a pull-in circuit for relay R4. Relay R4 will pull-in and open its contact R4-1 to open the holding circuit for relay E4 thereby causing relay E4 to become deenergized and, after a short delay, to drop-out. Drop-out of relay E4 causes drop-out of relay EP4 and relay T4, and also extinguishes indicator lamp L41. Drop-out of T4 will cause flasher relay F4 t0 drop-out and the relay assembly RA4 would return t0 a rest condition.

Returning to the original assumption of normal operation of the tracking system, when the vehicle proceeds into the radiant energy beam of the last detection station of the series, the relay D5 will become energized and pull-in and cause relay DPS to become energized and pull-in. Relay LS will become energized but not pull-in and relay E5 will become energized and pull-in thereby opening the energizing circuit of relay L5 at Contact ES-Z. Relay E5 Will pull-in through a circuit from a positive supply through contact RS-l, the coil of relay ES, contact DPS-4, lead 536 t0 RA4, lead 43?, contact EP4-1 to ground. Relay DPS will open its contact DPS-3 and open the holding circuit of relay E4, relay E4 holding in during its delay fall out period.

With both relay E4 and E5 pulled-in relay EA4 will become energized and pull-i n.

The indicator lamp Relay EPS will pull-in via contact ES-S and relay TS will become energized via contact ES-4 but relay TS will not pull-in. Indicator lamp L51 will become illuminated and both indicator lamps L41 and LS1 will then be illuminated.

Relay E4 will drop-Out after the delay period and extinguish indicator lamp L41 and drop-out relays EA@ and EP4 and deenergize relay T4 thereby returning relay assembly RA4 to a rest condition.

Relay E of RAS will be held in through its holding circuit including contacts RS-l, ES-l, E1S2 and DPS-2 to ground. The lead 53S of RAS extending to the right would be open so that the alternate holding circuit extending into an adjacent relay assembly, similar to other E series relays to the left, would not be completed. Relay EAS will not become energized since its energizing circuit is open at lead 523.

Now as the vehicle passes out of the beam of DETS actuation will cease and relay D5 and DPS will become deenergized and drop-out in order. Relay ES having been held in through the holding circuit including contact DPS-2 will now become deenergized as relay DPS dropsout. Relay ES will drop-out after a short delay and will cause drop out of relay EPS and deenergization of relay T5 and also will extinguish lamp LS1, the relay assembly returning to a rest condition.

It may occur that one of the detection stations, other than the rst or the last detection station in the series may fail to respond to actuation of its associated detector or that the detector itself may fail to respond to passage of a vehicle so that actuation does not occur.

Under such conditions the last actuated detection station before the detection station so failing, hereinafter referred to as skipped, will maintain its relay of the E series held in for a longer period of time since, due to failure of the skipped detection station, the holding circuit of the last energized relay of the E series will not be opened by the relay of the DP series of the skipped detection station. The relay of the E series of the detection station last actuated before the skipped detection station Will remain pulled in while the vehicle proceeds toward the beam of the detection station after the skipped detection station. In the preferred embodiment, the delayed time of the T series relay is adjusted so as to be just slightly longer than the normal travel time of a vehicle traveling from one detector beam to the next or adjacent detector beam. Thus under such conditions the delayed time would ordinarily be exceeded. At the end of the timed period of the relay of the T series time delay relay T will pull-in and cause the relay of the F series to pull-in and open and close its contact so that the indicator lamp will flash. The skipped detection station will provide no indicator while the next detection station (the detection station after the skipped detection station) will respond as if normal operation of the system had precedeed its actuation. The pullin circuit of the directional (E series) relay of the detection station after the skipped detection station will be completed through operation of the relay of the E1 series of the last operated detection station, before the skipped detection station, through the associated EA series relay of the last operated detection station.

Let it be assumed that a vehicle enters the controlled path and proceeds through the first (RAl) the second (RAZ) and the third (RA3) detection stations and that relay E3, EP3, and T3 are energized with E3 and EP3 pulled in and indicator lamp L31 illuminated and relay assemblies RAI and RA2 returned to rest.

Further assume that the vehicle passes into the radiant energy beam of detector DET4 and there is a failure within the fourth (RA4) detection station so that relay assembly RA4 fails to respond.

The relay EA3 of RA3 will remain deenergized since contact E4-8 of RA4, in the energizing circuit of relay EAS, will remain open due to relay'E4 remaining deenergized. With relay EA3 of RA3 remaining deenergized contact EA3-2 in the pull-in circuit of relay E13 will remain closed. Upon subsequent actuation of detector DETS the relays DS and DPS of RAS will pull-in and contact DPS-7 will close to complete the energizing circuit for relay E13 of RA3 from positive power through contact E3-9, the coil of relay E13, contact EAS-2, lead 324 to RA4, leads 424' and 425 to RAS, lead 52S and contact DFS-7 to ground. Relay E13 will pull-in and close its contact E13-1 and open its contact E134 to open the holding circuit of relay E3.

The energizing circuit for the relay ES of RAS will be completed from positive power via contacts Riel, the coil of relay RS, contact DPS-4, lead S30' to RA4, lead 430, lead 431; .to RA3, lead 331 to contact E13-1. Thus the relay assembly RAS may react to actuation and maintain continuity of tracking.

The relay E13 opens its contact E13-2 and breaks the holding circuit of relay E3, the relay E3 becoming deenergized. After a short delay relay E3 drops-out. When relay E3 drops-out contact E3-9 opens and breaks the pull-in circuit of relay E13 and relay E13 drops-out. Drop-out of E3 deenergizes relay T3 which drops-out and deenergizes relay F3. Drop-out of E3 also extinguishes lamp L31. Thus the relay assembly RA3 returns to a rest condition.

A skipped detection station condition may then be indicated by the illumination of the indicator of the detection station before the skipped detection station with the indicator steady for the time delay period of the associated T relay, followed by the dashing of such last indicator of the detection station before the skipped detection station, with the flashing illuminated indication held until reset through operation of the detection station after the skipped detection station.

Another function of the EA series relays and the WA series relays is to permit vehicles to travel or proceed close behind one another without losing tracking contnunity of the second or following vehicle of two Vehicles. The EA series relays permit close travel from left to right or eastbound and the WA series relays permit close travel from right to left or westbound.

Referring particularly to the EA series relays, it was previously stated that when two adjacent detection stations are actuated, by two eastbound vehicles, one detection station (RA4, for example) by one vehicle and an adjacent detection station (RA3, for example) by a second or following vehicle the relay of the EA series of the RA3 relay assembly relay EA3 will be energized.

Relay E3 of RA3 will be energized and pulled-in, as previously described, by the second or following vehicle actuating the detector DET3 and relay E4 of RA4 will be energized and pulled-in, as previously described, by the first or forward Vehicle actuating the detector DET4.

With both relays E3 and E4 pulled-in the relay EA3 will be energized and pulled-in via a circuit traced from positive power through contact E39, the coil of relay EAS, lead 323 to RA4, lead 423', contact E4-8 to ground.

Relay EAS closes its contact EA3-1 and completes a holding circuit and opens contact EAS-2 in the pull-in circuit of relay E13.

Thus the first or forward vehicle may move out of the detection station of which RA4 is a part and move forward into and actuate the detection station of which RAS is a part without causing energization of relay E13, although contact DPS-7 may be closed.

Thus the relay E13, which if pulled-in would cause drop out of E3 and loss of continuity of tracking of the second or following vehicle, is held deenergized so as to permit actuation of adjacent detection station by closely following vehicles without loss of continuity of tracking of the second or following vehicle.

The function of the WA series of relays is similar to that described for the EA series of relays except the WA series of relays are associated with right to left or westbound travel and the WA series relays are energized by pull-in of two vW series relays of -two adjacent detection stations and prevent pull-in of the WI series relay of the relay assembly operated by actuation of its detector by the second or following vehicle.

t may also occur that a vehicle may enter upon the controlled path at a point somewhere between the end sections so as not to actuate the initial detection station in the series into operation. Let it be assumed that a vehicle enters upon the path at a point between, for example, the detector DET2 and detector DETS and proceeds along the path so as to actuate detector DET3.

Upon actuation of the detector DET3 relay D3 will become energized and pull-in followed by relay DPS. Relay L3 will become energized and delay its pull-in to permit either relay E3 or W3 to pull-in, however, relay E3 will not pull-in because of open contacts LZ-6, and EP2-1 of RAZ and Ell-1 of RAI in its energizing circuit and relay W3 will not pull-in because of open contacts WP4-1 and L4-7 of RA4 and open contact lVl 5-1 of RAS in its energizing circuit. Therefore the relay L3 will pull-in and hold through its holding circuit previously described, and energize relay T3 and also energize relay F3 via contact L3-3 which completes a circuit from a power `supply through closed switch SW23 (SWVZ in FIG. 5), (since detection station of which RA3 is a part, is not the rst or the last detection station, switch SW23 of RAS is closed), contact L3-2 the coil of relay F3 to ground. Relay L3 will also illuminate indicator lamps L31 and L32, via closure of contacts L3-4 and L3-S (L-4 and L-5 in FiG. 5) which will now flash.

The vehicle may proceed to the right and actuate detector DET4. Upon closure of DET4 the detector relay D4 and the repeater detector relay DP4 will become energizing and pull-in. The relay L4 will become energized but not pull-in because of the delay on pull-in and relay E4 will become energized and pull-in because of contact L3-6 of RA3 in its pull-in circuit being closed. Relay L4 will have its energizing circuit broken and become deenergized and relay assembly RA4 will respond as if normal entrance onto the system had been made. Relay assembly RA3 will return to a rest condition upon drop-out of relay L3 via open contact EP4-2 in its holding circuit. When relay L3 drops out it will cause relays T3 and F3 to drop out and will extinguish indicator lamps L31 and L32.

As the vehicle proceeds along the path and actuates the next detector of the next detection station, normal tracking of the vehicle occurs, to termination, as previously described.

Let it now be assumed that a vehicle approaches the controlled path from its right hand end and is traveling westbound, for example, and that it enters the radiant energy beam of detector DETS of the detection station of which relay assembly RAS is a part. Upon actuation of the detector DETS and closure of its contact, detector relay DS is energized and pulls-in and operates its contacts to cause relay DPS to become energized and pull-in via contact DS-l and cause relay LS to become energized via contacts RS-l, DS-Z, E52 and lVS-1. Relay L5 does not immediately pull-in due to its delay on-pullain characteristic. Relay ES will remain deenergized because of open contacts L4-6 and EP4-1 of RA4 and E13-2 of RAS in its energizing circuit. Relay WS will remain deenergized since its energizing circuit through lead S29 is open. Relay L5 will pull-in and close its holding circuit through contacts RS-1, LS-l, lead S34' to RA4, lead 434, contact WP4-2, lead 437 to RAS, lead S37', lead S36 to the ground connection of the terminal which is made as part of the terminating section connections.

Operated relay LS will cause energization of time delay relay TS, and illumination of indicator lamps LS1 and L52. The switch SWZS of RAS (SW2 of FIG. 5) will 3Q be open since it is a part one of the two end detection stations.

As in each case, passage of the vehicle out of the detector beam will cease actuation of the associated detector and result in deenergization of relay DS followed by deenergization of relay DPS while relay LS holds in.

Proceeding forward, to the left, the Vehicle will enter the beam of detector DET4 and cause actuation of the detector resulting in completion of the energizing circuit for relay D4 via contact DET4 and relay D4 will pull-in and close its contacts and cause energization of relay DP4.

Operated relay D4 closes the energizing circuit for relay L4 at contact D4-2 which does not pull in immediately and also closes an energizing circuit for relay W4 which is completed from positive power via contact R4-1, the coil of relay W4, contact 134-4, lead 429 to RAS, lead S29 to contact ILS-7 to ground, and relay W4 pulls in immediately.

Energized relay VM opens the energizing circuit of relay L4 at contact W4-1 and closes contact W4-7 to energize relay Vv'P4. Closure of contact W4-3 (contact W3 in FlG. 5) provides an illuminating circuit for indicator lamp L42 and closure of contact W4-4 completes an energizing circuit for time delay relay T4.

Energized relay WP4 opens its Contact WP4-2 which causes relay LS of RAS to become deenergized. Relay LS holds in for its delay period and at this time lamps L51 and L52, and lamp L42 are illuminated.

Relay LS drops out at .the end of its delay period and deenergizes relay TS and extinguishes indicator lamps LS and L52.

Energized relay llt/4 also closes contact W4-5 which is inthe energizing circuit of relay C4. Relay C4 is connected to a ground return and is looking for a positive supply through contact 'W4-S and lead 426. Positive current may be supplied through certain contacts controlled in each relay assembly to the left, by the contacts of the associated relay of the E series through the associated relay of C series.

lt should be understood that each of `the relays of the W series of each respective relay assembly, upon pull-in, closes contacts to prepare an energizing circuit for its associated relay of the C Series while each of the relays of the E series of each respective relay assembly upon pullin closes contacts to prepare an energizing circuit for its associated relay of the C series.

Contact W4-S is closed by N4 and prepares a circuit to pull in relay WA4 but contact W3-9 of RAS is open to keep relay W'A4 deenergized.

As the vehicle proceeds westbound, for example, and exits from the beam of DET4 actuation closes and relays D4 and DP4 drop out. When the vehicle enters into the beam of detector DETS, closure of contact DETS, through actuation results in energization and pull-in of relay D3 of RA3 which closes its contacts and pulls-in relay EP3. Relay L3 will become energized via contacts RS-l, D3-2, E3-2 and VVS-1 as previously described but will not immediately pull-in. Relay W3 is energized from positive power via contactR3-1, the coil of relay W3, contact D3-4, lead 329 to RA4, lead 429 and contact VVP4-1 to ground, and immediately pulls in.

Relay W3 opens contact W3-1 and causes relay L3 to become deenergized.

Contact W3-7 is closed to energize and pull in relay WP3.

Contact W3-9 is closed and completes a circuit to energize and pull-in relay VA-4 of RA4 via contact W4-S, lead 42:0 to RA3, lead 320 and contact W3-9.

Energized relay W3 also closes contact W3-4 to energize time delay relay T3 and closes contact W3-3 to illuminate indicator lamp L32.

Energized relay EP3 opens contact DPS-5 which opens the holding circuit for relay W4 of RA4.

Contact W3-4 is closed by relay W3 to close the holding circuit for relay W3 rom positive power via contact 

1. IN A TRACKING SYSTEM FOR AIRCRAFT TRAVELING ALONG A PREDETERMINED PATH, A SERIES OF AIRCRAFT ACTUATED DETECTION STATIONS SPACED ALONG SAID PATH, AN INTERCONNECTED RELAY SYSTEM FOR SAID SERIES OF STATIONS AND INCLUDING FOR EACH DETECTION STATION, FIRST RELAY MEANS OPERABLE FOR PROVIDING AN OUTPUT INDICATIONS OF AN AIRCRAFT TRAVELING IN A FIRST DIRECTION IN RESPONSE TO A SEQUENCE OF ACTUATIONS BY SAID AIRCRAFT AT A SUCCESSION OF SAID DETECTION STATIONS INCLUDING THE STATION WITH WHICH SAID FIRST RELAY MEANS IS ASSOCIATED AND A PRECEDING STATION IN SAID FIRST DIRECTION, SECOND RELAY MEANS OPERABLE FOR PROVIDING AN OUTPUT INDICATION OF AN AIRCRAFT TRAVELING IN SECOND DIRECTION OPPOSITE TO THE FIRST IN RESPONSE TO A SEQUENCE OF ACTUATIONS BY AN AIRCRAFT AT A SUCCESSION OF SAID DETECTION STATIONS INCLUDING THE STATION WITH WHICH SAID SECOND RELAY MEANS IS ASSOCIATED AND A PRECEDING STATION IN SAID SECOND DIRECTION, ALARM CIRCUIT MEANS, AND ADDITIONAL RELAY MEANS INCLUDING CIRCUITS CONTROLLED BY THE SEVERAL FIRST AND SECOND RELAY MEANS FOR THE SERIES OF DETECTION STATIONS FOR OPERATING SAID ALARM CIRCUIT MEANS IN RESPONSE ONLY TO CONCURRENT OPERATION OF SAID FIRST RELAY MEANS FOR ANY ONE OF SAID STATIONS AND ONE OF SAID SECOND RELAY MEANS FOR ANY OTHER OF SAID STATIONS SUCCEEDING SAID ONE STATION IN SAID FIRST DIRECTION. 